1. Field of the Invention
The present invention relates to medical procedures in which an invasive device is inserted into a living body, and more particularly concerns the tracking of such a device with the use of radiofrequency fields.
2. Description of Related Art
X-ray fluoroscopes are used routinely to monitor the placement of invasive devices during diagnostic and therapeutic medical procedures. Conventional X-ray fluoroscopes are designed to minimize X-ray dosage. Nevertheless, some procedures can be very long and the accumulated X-ray dose to the patient can become significant. The long term exposure of the attending medical staff is of even greater concern since they participate in these procedures regularly. This is also a problem with other types of ionizing radiation such as positron emission tomography (PET), gamma ray camera and computed axial tomography (CAT) procedures. Consequently, it is desirable to reduce the overall ionizing radiation dose to all persons during these procedures.
Methods to track invasive devices without the use of X-rays have been disclosed previously in the aforementioned patent applications Ser. No. 07/753,563 and Ser. No. 07/753,565 hereby incorporated by reference. These applications describe systems in which an invasive device incorporating a radiofrequency coil is placed within a living body and its position is followed by either detecting or broadcasting a radiofrequency (RF) signal.
While systems employing invasive RF devices which must be plugged into a control unit to be tracked are feasible, it would be more desirable to have a system which employs invasive devices that do not require physical connection to the control unit while being tracked.